The 24-hour specialist counselling service, called Teacherline, aims to save £18m a year through lower absenteeism and sickness rates among teachers in schools in England and Wales.

The BBC's Susanna Reid: "It could save jobs and money"

It has been launched by the charity TBF - Teacher Support Network, with £250,000 funding from the Education Department for the first six months of its existence, and voluntary contributions from the teaching unions.

Organisers say it will provide practical and emotional support to teachers unable to cope with the demands of their job, including high public expectations, constantly changing education legislation and the strain of coping with unruly pupils.

The latest government figures show that 4% of the 450,000 teachers employed in England and Wales are suffering from depression.

'Constant scrutiny'

Patrick Nash, Chief Executive of TBF - Teacher Support Network, said the belief often expressed that teaching was an easy job was "farcical".

He believes the pressures on teachers have led many to suffer low self-esteem, loss of confidence in the classroom, relationship break-ups, and alcohol and drug dependency.

"Teachers play an important role in society and it is vital their needs are recognised and supported wherever possible," he said.

"They are subjected to constant scrutiny by the government, parents and the media, and are under pressure to get better results year on year and keep up-to-date with changing education policy.

"The majority of teachers regularly work a 10 to 12-hour day, which not only includes the time spent in the classroom but also the added extras such as lesson preparation, dealing with irate parents and departmental meetings.

"In the last 10 years teachers have seen a constant shift in goal posts as far as their jobs are concerned, but they are also supposed to be managers, financiers and social workers.

"Worse still, the pressure shows no sign of letting up - it is more difficult to be a teacher than it has ever been."

Staffed by former teachers

Tom Lewis, head of the Teacherline counselling service, and a former deputy headmaster, said 15,000 people were expected to ring the helpline during its first year. In its first week it has had about 30 calls.

"One of the great things about the helpline is that it is mainly staffed by ex-teachers who understand the pressures staff are under," Mr Lewis said.

School Standards Minister Estelle Morris said: "Teacherline will provide valuable support for teachers and the government is pleased to be able to support it."

The freephone Teacherline number is 08000 562561.